Signaling system



' Feb. 2, 1943. LE 2,310,034

SIGNALING SYSTEM F iled April 15, 1941 v 2 Sheets-Sheet 1 I h FIG.

/Nl ENTOR AH. M/LLEP B (/6 ATTORNEY Feb, 2,"1943. I v A. H. MILLER 2,310,034

' SIGNALING SYSTEM Filed April-l5 1941 2 Shee ts-Sheet 2 JNVE/VTOR v4. H M/LLE/P A 7709M? V Patented Feb. 2, 1943 ram orrics SIGNALING SYSTEM Albert H. Miller, Bayside, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New 1 York, N.' Y., a corporation of New York Application April :15; 1941, Serial No. 388,590 jlClaim. (o1. 177-340) This invention relates to signaling systems and more particularly-to signaling systems provided with answer-back'signaling means.

The object of the invention is'to provide a signaling systemsuitable for use in train dispatching and in which distinctive answer-back signals will be sent to the dispatcher to indicate conditionsof the system.

'A feature of the invention resides in the means provided for remotely controlling the connection and disconnection of the signaling system of one line to the signaling system of another line.

Another feature resides in the means provided for sending distinctive answer-back signals to the dispatcher originating the call connection.

Other'features reside in the particular combination of the apparatus parts involved.

In the drawings:

Fig. 1 shows a schematic diagram of the systemadapted for one-way operation by a single dispatcher;-and

Fig. 2 shows" a schematic diagram of the 'sy's tern adapted for two-way operation.

The system shown in Fig. 1 may be used by a train dispatcher in remotely controlling the connection of a branch line signalling system to the signaling system normally used by the dispatcher in selectively calling way stations on the railroad line over which he normally has control. 7

The system shown'in Fig. '2'may be used in remotely controlling the connection of the signaling' systems of two railroad or Signaling systems of two divisions of a railroad, the connecting of the twosystems being s'eparatelycontrolled by either one or the other of the two train dispatchers.

- In the systems shown and hereinafter described distinctiveanswer-back signals are sent to the'd' spatcher originating the 'call connection to inform him when the required connection or d sconnection of the lines has been accomplished.

The connection and disconnection operations are con rolled by'the dispatcher through the op eration of code signal sending keys at. the dispatchers station and impulse operated selectors and relays. The selectors and relays may be located at some point remote from the dispatchers station and where conductors of the branchline or other signaling line are arranged to be brought into signaling connection with the dis- Da hers signaling system. i The. code signal sending keys operate toc'onrol the sending of impulses to operate the selectors and ma be of some well-known type such. for instance. as the impulse transmitter shown and des ribed in J. C. Field Patent 1,306. 654 issued June 10; 1919 The selectors may be of e welbk'oown type such, for instance, as the selectors shown and described in J. C. Field Patent 1,343,256 issued June 15, 1920. It will be as sumed for th purpose of I simplifying this description that the "code signal sending keys and the selectors are of the types shown and described in the above-mentioned Field patents.

In Fig. '1, 3 indicates'the train dispatchers station apparatus, 4 the signaling system of 'a main line of the railroad, 5 a signaling line of a branch line of the railroad and 6 a remote station at which connection is to be made between the main line signaling system and the branch line signaling system, the remote station apparatus being shown as occupying the space defined by the dot-dash lines 1.

The dispatcher at station 3 normally uses the signaling system 4 comprising the main line conductors 8 and 9 to send signals to way stations, not shown but which are located out alon the main line system, each way station havin located thereat an impulse operated selector and the dispatcher having at his station a separate codesignal impulse sending key or some other impulse sending device to control operation. of the'selectors, all of which is well known in the art and disclosed in the J. C. Field Patent 1,343,-

In the present invention and. as shown in Fig. l, the dispatcher at station 3 may bring into connection with the mainline signaling system 4, a branch line 5 comprising the conductors l0 and l I leading to and having suitable connection with way station apparatus, not shown but which may be located at a station or stations on the branch line.

- When the dispatcher at station 3 desires to bring the branch line 5 into communication with the main line system, he operates a'code signal impulse sending key l2. The code signal sending key I2, as clearly described in the J. C. Field Fatent '1,306,054, is provided with teeth, certain ones of which may be blocked out by one or both adjustable cams l3 and M to obtain a particular number and combination of effective teeth for calling purposes. The key is adapted to rotate in the direction of the arrow and the teeth thereon are provided to move contact springs l5 and IS in circuit with the pole changing relay H. The free ends of the contact springs l5 and I6 are bentdownward and an insulating roller 18 is provided on the free end of the contact spring Hi. This insulating roller is engaged by the cam 3 to separate the contact springs I5 and I6 duringthe passage of the cam l3 under the roller 18.

Conta'ctof the spring It with thetoothed wheel it closes a circuit for relay 20 which, uponenergiz ation; connects the battery 2| to the main line system 4 comprising the conductors 8 and 9. H The teeth on the wheel 1 B-cause alternate closing and opening of the contact springs-l5 and lBso that the 'pole changing relay I1 is alternately energized and deenergized to reverse the connection of the battery 2| relative to the conductors 8 and 9. Operation of the pole changing relay controls the operation of the selector 22, the electromagnets 23 of which are alternately energized and deenergized over the conductors 8, 9, 24 and 25 and through the condenser 26 to step the wheel 21 in the direction of the arrow. The Wheel 21 is equipped with holding pins 28 which are engaged by the upper end of a holding contact spring 29 to hold the wheel 2'! against reverse movement at certain predetermined positions. A spring contact 39 is rotated with the Wheel 2'! to engage a fixed contact 3| or 32 according to the particular number and combination of impulses received by the selector 22. Assuming that the .code sending key 2 is set to send a series of impulses-divided into groups of 8-5-4 and that the selector 22 has its holding pins 28 set so that the contact 39 will be on contact 3| on the last impulse, the apparatus at the station 6 will be operated to connect the branch line to the main line 4. The selector 22 and the code sending keys provided forcontrolling the operation of the selector are constructed and arranged so that the selector will remain on the selected contact 3| or 32 for a brief period known as the ringing period, and will then restore to normal position.

When the spring contact 39 of the selector 22 makes contact with the fixed contact 3|, a bell 33 or other signaling device having self-interrupter contacts 34 therein is energized. Simultaneously with the energization of 'the bell 33 a relay 35 and a mechanical locking relay 48 are energized to bring the branch line 5 into signalingconnection with the main line '4. The circuit for energization of the bell 33 and the relay 35 may be traced as follows: local battery 36, conductor 37, operating winding 38 of relay 35, conductor 44 to conductor 39, winding of bell 33 and self-interrupter contacts 34 of bell 33, conductor 40, conductor 4| fixed contact 3| and contact spring 39 of selector .22, wheel 21 and holding spring 29 of selector 22, conductors 42 and 43 to battery 36. Relay v35 is held against deenergization when the self-interrupter contacts 34 of the bell 33 are opened through a holding circuit which may be traced from battery 36, through conductor 31, operating winding 33 of relay 35, conductor 44, resistance 45, conductor 46, wheel 21 and holding spring 29, conductors 42 and 43 to battery 36.

The relay 35 is equipped with anextra winding 41 which is in inductive relation with the operating winding 38 but is not part of the operating winding. When the relay 35 and the mechanical locking relay 48 are simultaneously operated. the winding 41 of relay 35 is connected in bridge of the main line conductors 8 and 9. The relay 48 may be of any suitable construction providing that it may be remotely controlled to lock contacts into a circuit closed condition and then remotely controlled to unlock the contacts made in its first operation.

The relay 48 as shown in the drawings is equipped with two operating windings 49 and 59, a pair of mechanically connected contact-armatures 5| and 52, a pivoted latch 53 and a release armature 54. When the relay 48 is operated, through energization of its lower winding 49, it pulls its armatures 5| and 52 into contact with the respective front contacts 55 and 56. The circuit for energization of winding 49 may be traced as follows: battery 36, conductor 84, winding 49 of relay 48, conductor 4|, contact 3| and spring contact 39 of selector 22, wheel 21, holding spring 29, conductors 42 and 43 to battery 36. Upward movement of armature 5| displaces the lower end of the latch 53 against the action of a spring 51. The displacement of the lower end of the latch is sufficient to permit the armature 5| to pass above abevelled hook 58 on the lower end of the latch so that the latch 53 will hold the armatures 5| and 52 in contact with the respective front contacts 55 and 56. Relay 35 being operated to pull its armature 59 against front contact 69, the extra winding 41 on relay 35 is in bridge of the line wires 8 and 9 of the main line signaling system. The circuit through the winding 41 may be traced as follows: conductor 8, conductor 6|, conductor 62, condenser 63, conductor 64, winding 41 on relay 35, front contact 69, armature 59, condenser 65, conductor 66, lower armature 61 and back contact 68 of relay 69, conductor 79, conductor 1|, front contact 55 and armature 5| of relay 48, conductor 12 and conductor 13 to main line conductor 9.

When the relays 35 and 48 have been operated as above described and the selector 22 is on contact 3| and the bell 33 is ringing a straight buzzer tone is produced in the telephone set I4 of the dispatcher at station 3 to indicate to the dispatcher that the apparatus at station 6 has been operated to bring the branch line 5 into communication with the main line 4, the buzzer signals being produced by operation of the self-interrupter contacts 34 in the bell 33 and being inductively transmitted from the operating winding 38 of relay 35 to the extra winding 4'1 on the relay 35. At the end of the ringing period the selector 22 is automatically restored to normal position, relay 35 becomes deenergized and releases its armature 59. The mechanical locking relay 48 is held however in a locked condition by the latch 53. The dispatcher at station 3 may now talk or otherwise transmit signals from station 3 to the branch line 5 it being understood that the dispatcher at station 3 has a transmitter or other signaling device in connection with the line wires 8 and 9 for communicating with the branch line 5 when the branch line -5 is brought into communicating condition with the main line 4. The talking or signaling circuit as shown in Fig. 1 is through the repeating coil -'l5 and the primary side of this circuit may be traced as follows: main line conductor 8, conductor 6|, lowermost armature 52-and front contact 56 of relay 48, conductor 16, primary winding of repeating coil 15, conductor H, front contact 55 and armature 5| of relay 48, conductor 12 and conductor 3 to main line conductor 9. The secondary side of the talking or signaling circuitis through the conductors l9 and of the branch line 5 and the secondary winding of repeating coil 15.

When the dispatcher at station 3 desires to disconnect the branch line 5 from communicative condition with the main line 4 he sends a set of signal impulses to operate the selector 22 to the fixed contact 32. This set of impulses may be sent by operation of a suitable code signal sending key at the dispatchers station 3. The code signal sending key 11 may be used for this purpose, the key being set to control the sending of the correct number and arrangement of impulses required to step the selector 22 around so that the spring contact 39 will come to rest on the contact 32. This closes a circuit for the bell 18 which is equipped with self-interrupter contacts 19. A circuit is also closed at the sametime ,to operate relay35 to pull armature 59 against front contact 60. The circuit for operating the bell l8 and relay may be traced as follows: battery 36, conductor 31, operating winding 38 of relay 35, conductor 39, winding and self-interrupter contacts 19 of bell I8, conductor 89, conductor 8|, contact 32 and spring contact 38 of selector 22, wheel 21 and holding spring 29, conductors 42 and 43 to battery 36. The selector 22 will hold on contact 32 for a brief period known as the ringing period and will then automatically restore to normal position. During the ringing period the bell 18 will be operated to alternately break and make its self-interrupter contacts 19 and relay 35 will be held against release of its armature 59 from front contact 68 by the holding circuit extending through its operating winding 38, the conductors 31 and 44, resistance 45, conductor 46, wheel 21 and holding spring 29 of selector 22. Simultaneously with the energization of the bell 18 and the relay 35 the mechanical locking relay 48 will be operated to release the latch 53 from its holding condition of armatures 5! and 52. The latch 53 is released by the pulling down of armature 54 against the action of spring 82, the armature 54 being pulled down when the upper winding 59 of relay 48 is energized and having a cam 83 hearing against the upper end portion of the latch 53. The upper winding of the relay 48 is energized when the spring contact 30 of the selector 22 comes to rest on the fixed contact 32. The circuit for the energization of the winding 59 may be traced as 'follows: battery 36, conductor 84, upper winding 59 of relay 48, conductor 8 l fixed contact 32, spring contact 33, wheel 21 and holding spring 29 of selector 22, conductors 42 and 43 to battery 38. Relay 48 is therefore operated to release the armatures 51 and 52 from engagement with the respective front contacts 55 and 56 and thus disconnect the branch line 5 from communicative condition with the main line signaling system 4. The bell 18 through its interrupter contacts 19 operates to produce a pulsating current in the operating winding 38 of relay 35 and this pulsating current is inductively picked up by the winding 41 of relay 35 and sent back to the dispatcher at station 3 to produce an answer-back signal. e

, This answer-back signal, however, is made distinguishable from the answer-back signal received by the dispatcher at station 3 when the branch line 5 was brought into connection with the main line system. The second answer-back signal and which will hereinafter be called the release answer-back signal is made distinguishable from the first answer-back signal by the operation of relays 69 and 85 which are operated in sequence when the spring contact 39 of the selector 22 is in engagement with contact 32. Relay 69 pulls up its lower armature 6'! from engagement with back contact 68 and opens the original answer-back circuit at this point. It also operates to pull the armature 61 against the lower front contact 86 and thus establish a new answerback circuit. This new answer-back circuit may be traced from conductor 8, through conductor 6|, conductor 62, condenser 63, conductor 64, winding 41, front contact 69 and armature 59 of relay 35, condenser 65, conductor 66, lower armature 6! and lower front contact 86 of relay 69, conductor 81 back contact 88 and armature 5| of relay 48, conductor 12 and conductor 13 to line conductor 9. The circuit for operation of relay 69 is as follows: battery 36, conductor '84,

conductor 89, back contact 98 and armature 9| of relay'85, conductor 92, winding of'relay 69, conductor 93, conductor 8|, contact 32, spring contact 30, wheel 21 and holding spring 29 of selector 22, conductors 42 and 43 to battery 36. Relay 69 pulls'its upper armature 94 against upper front contact 95 and closes a circuit for relay through conductor 96, and relay 85 then operates to pull its armature 91 away from back contact 99 and thus open the energizing circuit of relay 69. It will be seen therefore that relays 69 and 85 operating in sequence continue to close and open the new answer-back circuit through the lower armature 61 and lower front contact 88 of relay 69. The release answer-back signal therefore is in effect broken up so that it will be head in a series of buzzer tones with distinct pauses instead of a continuous buzzer tone, It is therefore readily distinguishable by the dispatcher at station 3 from the first answer-back signal received and assures him that the branch line 5 has been disconnected from the main line signaling system.

The dispatcher at station 3 normally uses the main line signaling system comprising the conductors 8 and 9 to selectively signal way stations on the main line. The way stations are not shown in the drawings in this case, however, because the showing of them is not essential to the description and understanding of this invention and their use is well known. The selectors at such way stations, however, could be brought into operation in selectively calling the way stations by the dispatcher operating a suitable code signal sending key such, for instance, as the code signal sending key 9! or keys at the points 98 and 99.

The system shown in Fig. 2 is designed to provide a means for interconnecting the signaling systems of two main line railroads or the signaling systems of two divisions of a railroad. This system employs the same kind and the same general arrangement of apparatus parts as the system shown in Fig. 1. The like parts in the two systems will therefore be identified by the same numerals. The system is arranged, however, to permit the interconnecting of the two signaling systems by the operation of apparatus under the control of either of the two train dispatchers. Each train dispatchers station is equipped with code signal sending means to separately control the connecting of the two signaling systems.

In Fig, 2, 3 indicates the train dispatchers station apparatus of one division of a railroad signaling system (east line), 4 the signaling system of the east division, I a signaling system of another division of the railroad (west line) and I96 a remote station at which the two divisions of the railroad signaling systems may be brought into connection, the remote station apparatus being shown as occupying the space defined by the clotdash lines I81.-

The dispatcher at station 3 normally uses the signaling system 4 comprising the main line conductors 8 and 9 to send signals to way stations, not shown, but which are located out along the east line system, each way station having located thereat an impulse operated selector and the dispatcher having at his station a separate impulse sending key cr some other suitable impulse sending device to control operation of the selectors, all of which is well known in the art.

In the present invention and as shown in Fig, 2 the dispatcher at station 3 may bring into connection with one division of the main line sig naling system 3 (east line) another division of the main line signaling system I95 (west line), comprising the conductors H9 and III leading to and having suitable connection with way station apparatus, not shown, but which may be located at a station or stations on the West line.

When the dispatcher at station 3 desires to bring the east line signaling system into communication with the west line signaling system he operates a code signal sending key I2. The key I2 is adapted to move its contact springs I5 and I6 into and out of circuit closing condition for the pole changing relay l1 and also closes a circuit to relay 29 which upon energization connects the battery 2| to the east line signaling system 4. The teeth on the wheel I9 cause alternate closing and opening of the contact springs I5 and I5 so that the pole changing relay I1 is alternately energized and deenergized to reverse the connection of the battery 2| relative to the conductors 8 and 9. Operation of the pole changing relay I1 controls the operation of the selector 22, the electromagnets 23 of which are alternately energized and deenergized over the conductors 8, 9, I98, I99 and I I 2 and through the condenser 26 to step the wheel 21 in the direction of the arrow. Assuming that the code sending key I2 is set to send a series of impulses to operate the selector 22 to a contact making position and that the selector 22 has its holding pins 28 set so that the contact 39 will be on contact 3 I on the last impulse the apparatus at the station I93 will be operated to connect the east line signaling system to the west line signaling system. The selector 22 and the code sending keys provided for controlling the operation of the selector are constructed and arranged so that the selector will remain on the selected contact 3| or 32 for a brief period known as the ringing period and will then restore to normal position.

When the spring contact 30 of the selector 2?. comes to rest on the fixed contact 3|, the bell 33 or other signaling device having self-interrupter contacts 34 therein is energized. Simultaneously, with the energization of the bell 33, the relay 35 and the mechanical locking relay 48 are energized to bring the east line signaling system into connection with the west line signaling system. The circuit for energization of the bell 33 and the relay 35 may be traced as follows: local battery 39, conductor 31, operating winding 38 of relay 35, conductor 44, conductor 39, winding of bell 33 and self-interrupter contacts 34 of bell 33, conductor 49, conductor 4|, conductor H3, fixed contact 3! and contact spring 39 of selector 22, wheel 21 and holding spring 29 of the selector 22, conductor 42 and conductor 43 to battery 36. Relay 35 is held against deenergization when the self-interrupter contacts of the bell 33 are opened through a holding circuit which may be traced from battery 35, through conductor 31, operating winding 39 of relay 35, conductor 44, resistance 45, conductor 46, wheel 21 and holding spring 29, conductor 42 and conductor 43 to battery 36.

The relay 35 operates to connect its extra winding 41 across the conductors I98 and I99 when the selector 22 is operated to a ringing position and the mechanical locking relay 48 is operated. The structure of the mechanical locking relay 43 has already been described in connection with Fig. 1. The circuit established by the operation of relay 35 and through contacts of the relay 48, may be traced as follows: conductor I98, conductor 92, condenser 53, conductor 64, extra winding 41 of relay 35, front contact 63 and armature 59 of relay 35, condenser 65, conductor 63, lower armature 61 of relay 69, back contact 63, conductor 19, conductor 1I, upper front contact 55 and armature 5| of relay 48 to conductor I99.

It will be seen that when relay 35 is operated to pull its armature 59 against contact 60 and when relay 48 has been operated to pull its armature 5| against contact 55 and 52 against 56 and the relay 43 is locked in this condition by means of the latch 53, an answer-back circuit is obtained to send signals to the train dispatcher who originated the call connection, the answer-back signals being produced by operation of the self-interrupter contacts in the bell 33 and being inductively picked up from the operating winding 38 of the relay 35 by the extra winding 41 on this relay.

At the end of the ringing period the selector 22 will automatically restore to normal position and relay 35 will release its armature 59 from contact with front contact 69 to break the answer-back circuit. The mechanical locking relay 48, however, will remain in a latched condition. The dispatcher at station 3 may then talk or otherwise signal to the dispatcher on the west line. The talking or signaling circuit established from the east line may be traced as follows: line conductor 8, conductor I03, lowermost armature 52 and front contact 53 of relay 48, conductor 15, primary winding of repeating coil 15, conductor 1I, front contact 55 and uppermost lower armature 5| of relay 48, conductor I09 and line conductor 9 of the east line signaling system. The telephone conversation or other signals sent by the dispatcher at station 3 are transmitted through the repeating coil 15 to conductors H4 and H5 leading to the respective line conductors I I9 and III of the west line signaling system.

By operating the code sending key 11 in the same manner as in Fig. 1 the dispatcher at station 3 may remotely control the apparatus at station I96 to disconnect the west line system from the east line system. In this case the selector 22 is operated to its fixed contact 32 to bring the bell 18 into operation and to again operate relay 35. Simultaneously with the operation of relay 35 the relay 48 is operated to release the latch 53. The circuit for operating the relay 48 to release its latch may be traced as follows: battery 36, conductor 31, conductor IIB, conductor II1, upper winding 59 of relay 48, conductor H8, fixed contact 32 of selector 22, spring contact 39, wheel 21 and holding spring 29 of selector 22, conductors 42 and 43 to battery 36. The circuit for operation of relay 35 and bell 18 may be traced as follows: battery 35, conductor 31, operating winding 38 of relay 35, conductor 44, conductor 39, conductor 88, winding of hell 13, interrupter contacts 19, conductor II9, conductor H8, fixed contact 32 of selector 22, spring contact 39, wheel 21, holding spring 29 and conductors 42 and 43 to battery 36.

When the upper winding 59 of relay 48 is energized the relay 48 will release the latch 53 to permit the armatures 5i and 52 to restore to normal position. Relay 35 will be operated to close its armature 59 against contact 69 and the bell 13 will be brought into operation to send the release answer-back signal. Relay 69 is brought into operation simultaneously with the operation of relay 35 and completes the release answer-back circuit through armature 61 and front contact 86. The release answer-back cir cuit may be traced through the extra winding 41 of relay 35, front contact 69 and armature 59. condenser 65, conductor 66, armature 61 and front contact 86 of relay 69, conductor 87, back contact 88 and armature 5I of relay 48, conductor I69 to line wire 9, the other side of the circuit being from line wire 8, conductor I08, conductor 62, condenser 63 and conductor 64 to winding 4! of relay 35.

Relay 63 is operated through a circuit involving the armatur 9| and back contact 90 of relay 85. The relays 63 and 85 are operated in sequence as explained in the description of Fig. 1 and break up the release answer-back signal so that it may be readily distinguished from the original answer-back signal, the release answer-back signal being heard in the dispatchers telephone set I4 at station 3 in the form of interrupted buzzer tones.

The dispatcher at the west line station I05 may bring the west line into communication with the east line by operating code signal sending keys at the station I05 in the same manner as the east line dispatcher at station 3 brought the two line systems into communication.

It will be understood that the code signal sending keys I20 and I2I at the west line station I05 are duplicates of the respective code signal sending keys I2 and 1! of the east line station 3. The keys I20 and I2I may be separately operated in the same manner as keys I2 and IT to control the operation of the apparatus at station When the key I20 is operated it brings into operation a line relay I 22 and the pole changing relay I23. Relay I22 connects the battery I24 to the line system comprising the line conductors I I and II I. Impulses sent over the line conductors H0 and III and through the conductors H4 and H step a selector I25 around to a contact making position. The selector I25 is a duplicate of the selector 22. The fixed contacts I26 and I2! of selector I25 correspond to the respective fixed contacts 3| and 32 of the selector 22. Operation of the selector I 25 to the contact I26 will cause operation of the bell 33, the relay 35 and the mechanical locking relay 48, the contact I26 being connected by conductor I28, to conductor M and the holding spring I29 being connected by conductor I30 to conductor 43.

When the selector I25 is operated by means of its electromagnets I3I to contact I26 the bell 33, relay 35 and the mechanical locking relay 48 are brought into operation. The answer-back signal produced will be transmitted back to the dispatcher at station I05 to indicate that the west line has been connected to the east line system, the answer-back signal being transmitted through the repeating coil I5, the primary side of which is connected by conductor I6 to the front contact 56 of relay 48 and by conductor III to the back contact 68 of relay 69. At the end of the ringing period the selector I25 will automatically restore to normal position, the bell 33 and the relay 35 will be deenergized but the relay 48 will remain in latched condition. The dispatcher at the west line station I05 may then have communication with the east line system through the repeating coil 15.

To disconnect the west line system from the east line the dispatcher at the west line station I05 will operate the code signal sending key I2I to operate the selector I25 to the contact I21.

The bell I8, relay 35 and the mechanical locking relay 48 will then be operated. Relays 69 and85 will also be brought into sequential operation to produce the release answer-back signal. The relay 48 on this second operation from the station I05 will release its latch 53 to release the connection originally established between the two line systems. It will be seen, however, that the uppermost armature I32 of relay 60 is in engagement with back contact I33 which through conductor I34 is connected to the primary of the repeating coil 15 and that this primary is also connected through conductor 10 to the back contact 68 of relay 69. During the ringing period the release answer-back signals will therefore be transmitted through the repeating coil I5 back to the dispatcher at station I05 to assure him that the mechanical locking relay 43 has been operated to release the connection originally established between the two lines. The release answer-back signal will be made intermittent by the sequential operations of relays 69 and 85. At the end of the ringing period the selector I25 will automatically restore to normal position, and the bell I8 and the relay 35 will be deenergized.

The east line and the west line systems may be equipped with'suitable code signal sending keys to operate selectors at Way stations not shown but which are located along the lines. The key 9! at station 3 is provided for this purpose and a corresponding key I35 is provided at station I05.

What is claimed is:

The combination with a main line signaling system suitable for use in train dispatching and a branch line system to be connected to said main line system, said main line system having connected therein a selector, two signaling devices operable to send answer-back signals over said main line signaling system, a two-winding relay operable on a first position of said selector to answer-back connect one of said signaling devices to said main line system and operable on a second position of said selector to partly make ready a circuit to answer-back connect the other of said signaling devices to said main line system and means to operate said selector, said signaling devices and said two-Winding relay, of a mechanical latching relay operable on a first position of said select-or to latchconnect said systems together and complete an answer-back circuit for the signaling device selected on the first position of said selector and operable on the second position of said selector to release the branch line system from connection with said main line system and partly complete a second answer-back circuit involving the signaling device selected by said selector on the second position of said select-or, means to operate said latching relay, a pair of sequentially operated relays operating on the second position of said selector and when said latching relay releases the branch line from connection with said main line, means to operate said sequentially operated relays, the first relay of said pair of sequentially operated relays operating to complete the second answer-back circuit and. the second relay of said pair operating to open the operating circuit of the first relay of said pair, and said pair of sequentially operated relays operating to intermittently close and open the second answer-back circuit to make the answerback signal sent on release of the connection be tween said systems distinguishable from the answer-back signal sent on connection of said systems.

ALBERT H. MILLER. 

